The field of the present invention relates generally to transducers, and more particularly to a force transducer for measuring force, which includes environmental protection for the sensor elements located and associated with the transducer.
The prior art is filled with numerous examples of force and pressure transducers. As one can ascertain, force and pressure are related and essentially pressure is determined in pounds per square inch while force would be determined in pounds. There are many different types of pressure and force transducers, but all have one thing in common in that they convert an applied force or pressure into stress in the plane of the sensors. These stresses can be conventionally measured and converted into electrical signals. The types of sensors vary, but the prior art discloses the use of piezoresistive sensors which are normally arranged in a bridge configuration.
In regard to this, the applicant herein, namely Kulite Semiconductor Products, Inc., has numerous patents related to pressure and force transducers and pressure sensor devices in general. For example, reference is made to U.S. Pat. No. 5,614,678, entitled, xe2x80x9cHigh Pressure Piezoresisitve Transducer,xe2x80x9d issued on Mar. 25, 1997, and assigned to Kulite Semiconductor Products, Inc., the assignee herein, by A. D. Kurtz et al. See also U.S. Pat. No. 5,955,771, entitled, xe2x80x9cSensors for Use in High Vibrational Applications and Methods of Fabricating the Same,xe2x80x9d issued on Sep. 21, 1999, to A. D. Kurtz, et al., and assigned to Kulite Semiconductor Products, Inc., the assignee herein.
In particular, the ""771 patent describes the use of semiconductor pressure transducers or force transducers which operate in harsh environments that may be corrosive or involve high temperatures or may be subjected to a high humidity or other deleterious environments.
A force transducer as indicated is a transducer which measures a force such as a pulling or pushing force. Such transducers are well known and can conventionally employ strain gages in the form of piezoresistive devices or other devices.
Based on the use of force transducers, the operating environment can be corrosive. In this manner, the prior art transducers or strain gages are protected by means of coating them with an epoxy or some other sealing element. Since the devices are normally exposed to air or exposed to the atmosphere in general, the devices can be subjected to moisture which can seep into the sealant and eventually corrode or otherwise destroy the strain gages, as well as abrasion and other physical effects, which would eventually over time create problems in transducer operations.
It is therefore an object of the present invention to provide a force transducer utilizing strain gages which are protected from outside harsh environments and can therefore increase the life and use of such a transducer.
A force transducer comprising a housing having a front and rear portions joined together by a platform, which platform is compliant compared to said front and rear portions and is adapted to receive an applied force which force causes said platform to tend to compress or expand as a function of the direction of said force applied force.
At least one sensor is mounted on said platform and operative to provide an output according to the extent of compression or expansion, and therefore according to the magnitude of said applied force.
a compliant tubular member is secured at one end to said front portion of said housing at said other end to said housing rear portion and positioned as secured to surround and enclose said sensor to thereby protect said sensor from the surrounding environment, said member expanding and contracting compliantly with said applied force to thereby enable said sensor to respond to said force substantially unimpeded by said tubular member.